Phagocytosis-associated functions in neonatal monocyte-derived macrophages

Using a Teflon culture system we analyzed different aspects of cell maturation and phagocytic activities in neonatal monocyte-derived macrophages. Morphological and cytochemical characteristics as well as the protein composition of neonatal macrophages were identical with those of adult controls; actin binding protein (265,000 Da), myosin (210,000), alpha-actinin (102,000) and actin (42,000) could be identified in cells from either source. All phagocytic functions were shown to be perfectly normal in neonatal macrophages when compared with adult cells: random migration, chemotactic response to zymosan-activated serum and formyl-methionyl-leucyl-phenylalanine, ingestion, and killing of Staphylococcus aureus, phagocytosis-associated chemiluminescence, production of oxygen intermediates (superoxide anion, O2-; hydrogen-peroxide, H2O2). Phorbol myristate acetate-stimulated O2(-)-generation by 1 x 10(5) macrophages was 11.8 +/- 4.7 nmol/h for neonates, and 10.2 +/- 3.9 for controls; production of H2O2 was 7.6 +/- 3.5 nmol/h in neonatal macrophages and 6.4 +/- 2.8 in adult controls. It is unlikely, then, that the increased susceptibility of human neonates to systemic bacterial infections can be related to an abnormality in the essential phagocyte functions of macrophages.